Nowadays, the amount of content broadcast in HD (High-Definition) is gradually increasing. Also, a video format having a still higher resolution (to be referred to as OverHD hereinafter) has been studied. OverHD content has a resolution of about 4000×8000 pixels or higher, and an expected display screen size is about 100 inches. The resolution of SD (Standard-Definition) content is 480×720 pixels, and that of HD content is 1080×1920 pixels. Therefore, when OverHD content is output without reducing its resolution, a high-presence video with a much higher definition than SD and HD can be provided to the user.
Even if an environment that can receive and display high-resolution video content such as OverHD content in each home is realized in the future, it is improbable that content with SD and HD resolutions will disappear immediately. For example, a large number of formats such as OverHD, HD, SD, and the like will be broadcast together for a number of years.
In existing television broadcasting, SD and HD contents are broadcast together in a single channel. There is a technique for displaying a video which informs the user of a video format name after a change of video formats occurs and allows the user to recognize the change of the video formats in a video display apparatus compatible with SD and HD (Japanese Patent Laid-Open No. 2002-354364 (D1)).
When displaying content with a resolution lower than the number of display pixels of a display apparatus, the display apparatus scales video of the content up so as to fully display the content in one of the vertical and horizontal directions of the display apparatus. For example, in the current broadcasting environment, a display apparatus that can display HD content may scale up SD content in the vertical direction and/or horizontal direction in order to display it. In this manner, the number of pixels of the display apparatus can be fully and effectively used, and the user can enjoy the content at a large display size.
However, when a simple scale-up process is performed in correspondence with the number of pixels of the display apparatus, blurred video often results. Note that the simple scale-up process means a scale-up process which generates interpolated pixels using the same pixels as neighboring pixels, and which generates interpolated pixels by calculating interpolated pixel values by linear interpolation using pixel values of neighboring pixels, and the like.
In particular, when a lower-resolution video such as SD content is scaled up and displayed in correspondence with the resolution of an ultra high-definition display apparatus capable of displaying OverHD content, a highly blurred image is displayed. Such phenomenon are conspicuous compared to cases wherein SD content is displayed in a large scale on a display apparatus capable of displaying HD content. In particular, when a user views SD content immediately after viewing OverHD content, he or she may feel as though he or she were experiencing trouble with the display apparatus or with his or her own vision.
By displaying a video that informs the user of the change in video formats, as described in D1, the user can recognize that a considerable alteration in display quality is caused by the change of the video formats. However, even by applying the technique of D1, the user is merely informed of only the fact that the format has changed. For example, when the degree of resolution alteration is large, for example, when the video format changes from OverHD to SD, the user may want to adjust the display method. However, if all that is displayed is the format name of the currently displayed content, the user cannot get information regarding how to adjust the display. This problem may become especially pronounced in the future as the number of available video formats increases.
In another method, low-resolution content may be displayed without being scaled up—in other words, without altering its resolution. In this case, display of a blurred image can be prevented. However, the display size is reduced, thus posing another problem. For example, when SD content is displayed without altering its resolution on an ultra high-definition display apparatus capable of displaying OverHD content having a resolution of 4000×8000 pixels, the display size (the ratio of the display area to the full screen) becomes about 1/100. For this reason, the user may be inconvenienced due to the small display size. A display area of about 99/100 of the display apparatus, in other words, most of the display area is not used for display, and the capability of the display apparatus cannot be fully used.